The present invention relates generally to log periodic dipole antennas and more specifically to a dual mode log periodic dipole antenna which is capable of producing sum and difference patterns for dipole element lengths of one-half wavelength and one wavelength respectively.
Log periodic dipole antenna structures are well known in the antenna art. A discussion of such structures may be found in "Broadband Logarithmically Periodic Antenna Structures," R. H. DuHamel et al, 1957 IRE National Convention Record, Part 1, pages 119-128, and "Log Periodic Dipole Arrays," IRE Trans. Antenna Propag., Vol. AP-8, pages 260-267, May 1960.
However, for use in monopulse and direction finding applications, two separate log periodic arrays are necessary to provide direction finding capability across the VHF band. Such antenna systems are typically bulky and the electrical characteristics of the two antenna are hard to match. In addition, single mode dipole antennas radiate only sum patterns and cannot provide phase information which is necessary in target detection applications.